Device Having a Pneumatic Actuating Cylinder, and Method for Controlling a Device of Said Type

ABSTRACT

The invention relates to a device having a pneumatic actuating cylinder ( 1 ), wherein the actuating cylinder ( 1 ) has at least one pneumatic piston ( 2 ) and a brake element ( 15 ) which can be actuated in an arbitrary manner and which is connected to the pneumatic piston ( 2 ) or to a component ( 3, 7 ) which can be moved by means of the pneumatic piston ( 2 ), wherein a movement of the pneumatic piston ( 2 ) can be braked or suppressed by an actuation of the brake element ( 15 ). The invention also relates to a method for controlling a device of said type.

The invention generally relates to a device having a pneumatic actuating cylinder in accordance with the preamble of Claim 1. The invention also relates to a method for controlling a device of said type in accordance with Patent Claim 7.

Pneumatic actuating cylinders are used as actuators in various applications. In the field of commercial vehicle technology (trucks, buses), an advantageous application involves realizing an automatic clutch actuation in conjunction with automated gearshift systems via a pneumatic actuating cylinder. This eases the burden on the driver. The shift processes can be completely automated. Since compressed air is already available in commercial vehicles, the use of a pneumatic actuating cylinder is more favourable than a hydraulic actuating cylinder.

The important aspect of clutch actuation, particularly in the area of the clutch biting point, is to be able to perform sensitive actuating movements by means of the actuating cylinder. Traditional vehicle clutches have a force/travel curve, which initially rises roughly linearly up to a maximum value lying roughly around the clutch biting point. On the other side of the maximum value, the characteristic curve falls off again more or less sharply. This has the effect that the pressure built up in the actuating cylinder to achieve the maximum force is too high to hold a position close to the maximum value once the maximum value has been exceeded. This has hitherto been taken into account by relatively complex control algorithms in the actuating cylinder pressure control, such that a relatively sensitive position setting in the area of the clutch biting point is possible. Alternatively, pneumatic valves for pressure control in the actuating cylinder having different aperture cross-sections are connected to one another in parallel, in order thereby to optimise the sensitivity of the setting.

The problem addressed by the embodiments of the present invention is that of specifying a device having a pneumatic actuating cylinder and also a method for controlling a device of said type, wherein with very little effort a sensitive position setting of the actuating cylinder is possible even with a non-linear counteracting force path of an object to be actuated by the actuating cylinder.

This problem is solved by the invention recited in Claims 1 and 7. The dependent claims indicate further advantageous embodiments of the invention.

The invention has the advantage of facilitating improved fine control in the positioning of the actuating cylinder, even with highly non-linear counteracting force paths, using an easily realized structural enlargement, namely through the provision of a brake element which can be arbitrarily actuated. The brake element which can be arbitrarily actuated may be realized in a variety of embodiments. Any components which allow selective braking or holding of the position of the actuating cylinder's pneumatic piston or else a component that can be moved therewith may be used. To this extent, the term “brake element” not only covers brakes in the traditional sense, but also all other elements which allow this kind of braking or holding of the pneumatic piston or of a component that can be moved therewith, wherein the brake element must be capable of arbitrary actuation. By means of the brake element, the pneumatic piston or a component movable therewith can be held in arbitrary positions.

A further advantage of the invention is that fewer valves are required to actuate the device than in solutions known in the art. So, for example, only one pneumatic valve is required to actuate the actuating cylinder and one valve to actuate the brake element, rather than four pneumatic solenoid valves, as was previously the case.

In accordance with an embodiment of the invention, the brake element has a double-acting hydraulic cylinder with a hydraulic piston. The hydraulic piston is mechanically connected to the pneumatic piston or a component movable by means of the pneumatic piston. The brake element also includes a valve mechanism which can be actuated arbitrarily in a hydraulic connection line between two hydraulic pressure chambers, which are formed on opposite sides to one another of the hydraulic piston. A hydraulic control volume is thereby added to the pneumatic actuating cylinder. The hydraulic control, volume may be relatively small in structure, due to the incompressibility of the hydraulic medium. In this case it is not necessary, in particular, for an elaborate complete hydraulic system with a pump to be provided, but simply a compact, self-contained system. In this way, the maintenance costs of the brake element can be kept down.

The addition of a hydraulic control volume has the advantage that hydraulic systems offer good control performance, particularly in that the hydraulic medium is incompressible and therefore allows selective braking and holding of the pneumatic piston at arbitrarily defined positions.

In accordance with another embodiment of the invention, the valve mechanism includes at least one open setting, in which the hydraulic pressure chambers are connected, and at least one closed setting, in which the hydraulic pressure chambers are closed off from one another. This permits defined holding of the pneumatic piston in arbitrarily predetermined positions.

In accordance with a further embodiment of the invention, the brake element has an arbitrarily actuatable brake with at least one brake lining, which is movable towards the pneumatic piston or a component movable by means of the pneumatic piston, particularly a piston rod, when the brake is actuated. This advantageously allows the use of the widest variety of designs for the brake. For example, the brake may be hydraulically actuatable or electromotively actuatable. In an advantageous embodiment, a pneumatically actuatable brake is used. The same pressure medium can thereby be used as the pressure medium for actuating the brake as for the actuation of the pneumatic actuating cylinder. This allows a particularly cost-effective realization of the arbitrarily actuatable brake element. The brake may be configured as a friction brake, for example.

In accordance with yet another embodiment of the invention, the pneumatic actuating cylinder is designed as a single-acting clutch actuation cylinder for actuating a vehicle clutch. This allows simple actuation of the pneumatic actuating cylinder with only one pneumatic valve.

In accordance with a still further embodiment of the invention, the following features are provided:

a) the pneumatic actuating cylinder has a working side and a rear side facing away from the working side,

b) the actuating movement of the pneumatic cylinder can be delivered at the working side to a component located in the vicinity,

c) the brake element is disposed on the rear side.

This allows a particularly compact structure of the device according to the invention, so that the device can easily be integrated into existing applications.

A method for controlling a device of the type described above provides the following:

a) insofar as the pneumatic piston is to be extended, a compressed air chamber of the pneumatic actuating cylinder is acted on by compressed air, whereupon the brake element is not actuated,

b) insofar as the pneumatic piston is to be retracted, compressed air is vented from the compressed air chamber, whereupon the brake element is not actuated,

c) insofar as the pneumatic piston is not to be moved, the brake element is actuated.

The advantage of this as compared with methods known in the prior art is that only a kind of servo control is required. The actual precise positioning may be achieved through actuation of the brake element. Only the force required to move the actuating cylinder, e.g., to disengage the clutch, is thereby provided by the compressed air.

In accordance with another embodiment of the invention, the brake element is actuated shortly before or upon attainment of a required position of the pneumatic piston or a component that can be actuated by means of the pneumatic piston. Safe, reliable positioning can thereby be achieved. A delayed reaction inherent in the brake element can be compensated for particularly by actuating the brake element shortly before the required position is reached. The method may be realized by corresponding software programming of an electronic control unit controlling the brake element, for example.

In accordance with a further embodiment of the invention, a vehicle clutch can be actuated by means of the pneumatic actuating cylinder. The brake element is actuated on reaching the disengaging position of the vehicle clutch.

The invention is described in greater detail below with reference to exemplary embodiments set forth in the appended drawings, in which

FIG. 1 shows a first embodiment of a device according to the present invention with a pneumatic actuating cylinder and

FIG. 2 shows a second embodiment of a device according to the present invention with a pneumatic actuating cylinder.

In the figures, the same reference numbers are used for corresponding elements.

A pneumatic actuating cylinder 1 can be seen in FIG. 1, which has a pneumatic piston 2. A piston rod 3 is connected to the pneumatic piston 2, the rod projecting from the actuating cylinder 1 to the right in the representation in FIG. 1 and serving to actuate an external object. In accordance with the exemplary embodiment, it is assumed that a vehicle clutch is actuated by means of the piston rod 3. The vehicle clutch is symbolised by an arrow 4 in the diagram; the arrow symbolising the direction of action of the counteracting force F exerted on the piston rod 3 by the vehicle clutch.

The actuating cylinder 1 has a compressed air chamber 10. The compressed air chamber 10 is connected to a compressed air source 6 via a pneumatic valve, e.g., in the form of an electromagnetically actuatable valve 5 designed as a 3/2-way valve. Instead of the valve 5 represented with two settings, a 3-setting valve may also be used, which also exhibits a pressure-retaining setting, in addition to the switch settings provided in the valve 5 shown.

By means of the valve 5, compressed air can be fed from the compressed air source 6 into the compressed air chamber 10 or from the compressed air chamber 10 into the atmosphere. Through a corresponding pressure setting in the compressed air chamber 10, a corresponding force is exerted on the vehicle clutch 4 via the pneumatic piston 2 and the piston rod 3, via which the vehicle clutch can be actuated in the disengagement direction.

On its side facing away from the piston rod 3, the pneumatic piston 2 has a rearward piston rod 7, which projects from the housing of the actuating cylinder 1. Likewise on the rear side 17, i.e., on the side 16 of the actuating cylinder 1 facing away from the piston rod 3, a brake element 15 is disposed, which has a dual-acting hydraulic cylinder 8. The hydraulic cylinder 8 is screwed or flange-mounted on the housing of the pneumatic actuating cylinder 1, for example. The hydraulic cylinder 8 has a hydraulic piston 9, which is connected to the rearward piston rod 7. Through the connection via the rearward piston rod 7, the pneumatic piston 2 and the hydraulic piston 9 always perform the same movements.

On the one side of the hydraulic piston 9 is arranged a first hydraulic pressure chamber 11 and on the other side of the hydraulic piston 9 is arranged a second hydraulic pressure chamber 12. The hydraulic pressure chambers 11, 12 are connected to a hydraulic valve 13 via hydraulic lines. The hydraulic valve 13 has two switch settings, namely an open setting, in which the hydraulic pressure chambers 11, 12 are connected, and a closed setting, in which the hydraulic pressure chambers 11, 12 are closed off from one another. The hydraulic valve 13 may be designed as an electromagnetically actuatable 2/2-way valve, for example. By actuating the electromagnets of the hydraulic valve 13, either the open or closed position may be activated.

In the connection line between the hydraulic valve 13 and the hydraulic pressure chamber 11, a throttle 14 is additionally disposed. The flow between the hydraulic chambers 11, 12 may be set at a desired value via the throttle 14.

FIG. 2 shows a second embodiment of a device with a pneumatic actuating cylinder, wherein the same comments apply in relation to the actuating cylinder 1, the pneumatic valve 5 and the compressed air source 6 as to the embodiment according to FIG. 1.

The brake element according to FIG. 2 has a brake which can be pneumatically actuated. The brake has a pneumatic actuating cylinder 20. The pneumatic actuating cylinder 20 has a pneumatic piston 21 and a piston rod 22, which is connected to a first brake lining 23. Via compressed air actuation of a compressed air chamber 27 of the actuating cylinder 20, the brake lining 23 can be pressed against the rearward piston rod 7 via the pneumatic piston 21 and the piston rod 22. A second brake lining 24 is arranged on the opposite side of the rearward piston rod 7 as the counter-bearing of the first brake lining 23. The second brake lining 24 is supported by a counter-bearing block 25, which is connected to the actuating cylinder 20 via a connection plate 26. The brake linings 23, 24 may act on the rearward piston rod 7 in the form of a friction brake, for example, and brake and hold this. The rearward piston rod 7 may also be roughened to improve the braking action or provided with a defined texture or grooves.

The compressed air chamber 27 of the actuating cylinder 20 can be connected via a second pneumatic valve 28, which can be actuated electromagnetically, either to the compressed air source 6 or to the atmosphere. In this way, pressure in the compressed air chamber 27 can be increased or reduced arbitrarily and the brake therefore actuated arbitrarily. 

1. A device having a pneumatic actuating cylinder (1), wherein the actuating cylinder (1) has at least one pneumatic piston (2), characterized in that the device has a brake element (15) which can be actuated in an arbitrary manner and which is connected to the pneumatic piston (2) or to a component (3, 7) which can be moved by means of the pneumatic piston (2), wherein a movement of the pneumatic piston (2) can be braked or suppressed by actuation of the brake element (15).
 2. The device according to claim 1, characterized in that the brake element (15) has a dual-acting hydraulic cylinder (8) with a hydraulic piston (9), which is mechanically connected to the pneumatic piston (2) or to a component (3, 7) movable by means of the pneumatic piston, and the brake element (15) also exhibits a valve mechanism (13) which can be actuated arbitrarily in a hydraulic connection line between two hydraulic pressure chambers (11, 12), wherein the hydraulic pressure chambers (11, 12) are formed on opposite sides to one another of the hydraulic piston (9).
 3. The device according to claim 2, characterized in that the valve mechanism (13) exhibits at least one open setting, in which the hydraulic pressure chambers (11, 12) are connected, and at least one closed setting, in which the hydraulic pressure chambers (11, 12) are closed off from one another.
 4. The device according to one of the preceding claims, characterized in that the brake element (15) has an arbitrarily actuatable brake (29) with at least one brake lining (23, 24), which is movable towards the pneumatic piston (2) or a component (3, 7) movable by means of the pneumatic piston, particularly a piston rod, when the brake (29) is actuated.
 5. The device according to one of the preceding claims, characterized in that the pneumatic cylinder (1) is designed as a single-acting clutch actuation cylinder for actuating a vehicle clutch (4).
 6. The device according to one of the preceding claims, characterized by the following features: a) the pneumatic actuating cylinder (1) has a working side (16) and a rear side (17) facing away from the working side (16), b) the actuating movement of the pneumatic cylinder (2) can be delivered at the working side (16) to a component (4) located in the vicinity, c)the brake element (15) is disposed on the rear side (17).
 7. A method for controlling a device according to claim 1, characterized by the following features: a) in so far as the pneumatic piston (2) is to be extended, a compressed air chamber (10) of the pneumatic actuating cylinder (1) is acted on by compressed air, whereupon the brake element (15) is not actuated, b) in so far as the pneumatic piston is to be retracted, compressed air is vented from the compressed air chamber (10), whereupon the brake element (15) is not actuated, c) in so far as the pneumatic piston (2) is not to be moved, the brake element (15) is actuated.
 8. The method according to claim 7, characterized in that the brake element (15) is actuated shortly before or upon attainment of a required position of the pneumatic piston (2) or a component (3, 7) that can be actuated by means of the pneumatic piston (2).
 9. The method according to claim 7 or 8, characterized in that a vehicle clutch (4) can be actuated by means of the pneumatic actuating cylinder (1) and the brake element (15) is actuated on reaching the disengaging position of the vehicle clutch (4). 